This invention relates to a color liquid crystal display having a film which functions as both an orientation layer and as a color filter. In such displays, the orientation layer controls the orientation of the liquid crystal molecules. The invention further relates to a method of manufacturing such films.
Japanese Published Unexamined Patent Application No. 59-29225 (Japanese Patent Application No. 57-138450) discloses the formation of a color filter by printing predetermined patterns of each color with ink compositions synthesized by mixing a resin known as polyimide with coloring materials such as azo or anthraquinone dyes. The ink is printed on each surface of a pair of glass substrates on which transparent electrodes are farmed. This application further discloses the use of the color filter as an organic orientation film. The formation of a color filter by printing polyimide on each surface of a pair of glass substrates is also disclosed. The printed polyimide forms a resin film, which is patterned using photographic technology. The resin film with the predetermined patterns is immersed in a solvent in which a colorant is dissolved to disperse the colorant in the resin film. Finally, the color filter is used as an organic orientation film.
Japanese Published Unexamined Patent Application (PUPA) No. 60-48020 (Japanese Patent Application No. 58-154803) discloses a color liquid crystal display having a color filter formed by mixing dyes in a polyimide based polymer on transparent electrodes formed on a glass substrate. The color filter is provided with a liquid crystal orientation by rubbing.
Although the methods described above are intended to produce a polyimide film which functions as both an orientation layer, controlling the orientation of liquid crystal molecules, and a color filter, it has been found that not all polyimides can be used as both a liquid crystal orientation layer and a color filter layer. For example, a diacid anhydride formed by bonding two molecules of trimellitic acid, or amide diamine synthesized from a dicarboxylic acid and a diamine cannot be used practically, even if dyes are mixed with these compounds, because of their poor liquid crystal orientation properties and poor spectroscopic light transmissivity.